This invention relates to a fastening device for securing any element or object to a wall or partition. This device is intended more particularly for fixing objects to hollow walls or to walls made of a relatively brittle material, notably chipboard or porous concrete.
This device is of the type wherein a tightening screw is provided inside a tubular plug of deformable material disposed between the screw head and a nut carried by the opposite end of the screw. On the other hand, on at least one portion of the plug length, a plurality of longitudinal weakening lines forming flexible splines between them are formed.
Under these conditions, when the screw is tightened for moving the nut towards the screw head, the plug is caused to expand, so that the flexible splines undergo a deformation and may even become loose in relation to each other, due to the weakening lines provided for this purpose. The distorsion of the plug and more particularly of the splines thereof is intended for anchoring the fastening device in the bore into which the same has been introduced.
However, in actual practice it was observed that the anchoring action obtained with plugs of this specific type is not always reliable, due to the fact that this action results only from the distortion of the deformable splines of the plug, which does not occur under the best possible conditions since the tightening nut can rotate in relation to the plug during the plug expansion.
Besides, in most instances, due to the resiliency of the plug material no tearing effect is observed within the weakening lines separating the adjacent splines of the plug. Therefore, these splines remain attached to one another and this precludes the possibility of producing a sufficient torsion of the splines on themselves in order to provide a really efficient fastening device. In fact, the plug is simply expanded and this is not sufficient for obtaining a fully efficient anchorage.